13 C Direct Detected NMR for Challenging Systems.

Thanks to recent improvements in NMR spectrometer hardware and pulse sequence design, modern 13 C NMR has become a useful tool for biomolecular applications. The complete assignment of a protein can be accomplished by using 13 C detected multinuclear experiments and it can provide unique information relevant for the study of a variety of different biomolecules including paramagnetic proteins and intrinsically disordered proteins. A wide range of NMR observables can be measured, concurring to the structural and dynamic characterization of a protein in isolation, as part of a larger complex, or even inside a living cell. We present the different properties of 13 C with respect to 1 H, which provide the rationale for the experiments developed and their application, the technical aspects that need to be faced, and the many experimental variants designed to address different cases. Application areas where these experiments successfully complement proton NMR are also described.